My Blender has no Header
While I have no immediate answer, here is how you can find out the cause of the problem:


Open a command line shell.
Navigate to where your Blender is installed.
On windows you can Shift RMB in the blender program folder (without any file selected) in Windows Explorer and select Open command window here.
On linux this step is only necessary if you have multiple version of blender installed, otherwise you can just run blender.
Call blender from the shell. On windows, type blender.exe. On linux, type  ./blender.


Now Blender starts and leaves messages in the commandline shell. You will probably see one or more error messages which may lead you to the cause of the problem.

You can try to force Blender to use factory-settings by providing the commandline option as follows:

blender.exe --factory-startup


Some possible causes are:


a broken Addon
An installation error like: "out of disk space", "no write permissions on disk", etc.
Wrong Python version in Path (i am not sure if Blender gets trapped by that)